The video appears to show workers bungling the slaughter of cows struggling to walk and even stand. Under federal regulations, sick animals cannot be slaughtered for human consumption.

The investigation will determine whether sick cows were slaughtered and whether meat products from the company should be recalled, said Justin DeJong, a spokesman for the USDA Food Safety Inspection Service.

The agency suspended operations Monday at Central Valley Meat Co. in Hanford after receiving the video Friday from the animal welfare group Compassion Over Killing. The footage shows animals bleeding and thrashing after being repeatedly shot in the head with a pneumatic gun in unsuccessful efforts to render them unconscious for slaughter.

Federal regulations say that to avoid unnecessary suffering during slaughter, animals must be rendered unconscious by a single shot to the head from a pneumatic gun that fires a bolt through the skull to pierce the brain.

In-N-Out Burger, a fast food chain, severed its ties with the company after learning about the situation. Mark Taylor, chief operating officer, said on Tuesday that the company acted immediately upon becoming aware it.

“As soon as we became aware of the allegations regarding Central Valley Meat Company and their handling of cattle, we immediately severed our supplier relationship with them. In-N-Out Burger would never condone the inhumane treatment of animals and all of our suppliers must agree to abide by our strict standards for the humane treatment of cattle,” Taylor said to The Associated Press in a written statement.

In-N-Out’s agreement with suppliers prohibits companies from shipping beef from sick animals. The agreement also includes standards on humane treatment of animals.

The USDA said investigators are trying to determine whether the cows in the video were just lame or sick, which would render them unfit for human consumption.

“That’s the main issue right now,” said DeJong of the USDA’s Food Safety Inspection Service.

Central Valley Meat Co., owned by Brian and Lawrence Coelho, declined to comment on the video, saying company officials had not seen it. On Tuesday the company hired a public relations firm, which issued a statement saying the company is cooperating with investigators.

“Central Valley Meat is working closely with the USDA’s Food Safety and Inspection Service to address animal-handling concerns arising from a covert video provided to USDA by an animal rights group. Central Valley Meat takes these issues very seriously and is now developing a plan of action to present to FSIS to remedy any potential violations of USDA guidelines. Based on our own investigation and 30 years of producing safe, high-quality US beef, we are confident these concerns pose no food safety issues. We take these allegations very seriously and will immediately address any concerns the USDA may have,” the company said.

The video taken by an undercover investigator for Compassion Over Killing also shows cattle lying in pens unable to move, and at least one unable to stand to leave a stock transportation trailer.

Some clips show cattle with swollen udders that are unable to keep their legs under them. Other footage shows a downed cow trembling and unable to stand even as workers try to pull her up by the tail.

Within hours of seeing the video, the USDA’s Office of Inspector General sent investigators who found evidence of “egregious inhumane handling and treatment of livestock.” The possibility that animals were being inhumanely treated caused officials to shut down the plant while the investigation unfolds.

The USDA had at least two inspectors stationed at the site, and federal officials, when asked whether there was evidence the inspectors had neglected their duties, said the investigation is ongoing.

The USDA received hours of videotape from the Washington D.C.-based animal welfare group, which said its undercover investigator was employed by the slaughterhouse and made the video over a two-week period in June and early July.

Four minutes of excerpts the animal welfare group provided to The Associated Press showed cows being prepared for slaughter. One worker appears to be suffocating a cow by standing on its muzzle after a gun that injects a bolt into the animal’s head had failed to render it unconscious.

In another clip, a cow is still conscious and flailing as a conveyor lifts it by one leg for transport to an area where the animals’ throats are slit for blood draining.

“The horror caught on camera is sickening,” said Erica Meier, executive director of Compassion Over Killing. “It’s alarming that this is not only a USDA-inspected facility but a supplier to the USDA.”

Online USDA records show the company has contracted to sell ground beef to USDA food programs.

“It’s a good sign that the USDA is taking this seriously, but I want to see what comes next,” said Meier of Compassion Over Killing, adding the video will be posted on the organization’s website.